Talk to some of the members of the Lyons' Pride in the Great Hall after gaining entry to the Citadel. They will tell you about a betting pool to try and guess Gallows' real name. You can ask Knight Captain Gallows about it after hearing about the bet. If your speech skill is high enough, you can convince Gallows to tell you his real name. After you find out his name you should speak to Paladin Glade, who is running the betting pool. Glade can be found near Gallows in the Great Hall in the A Ring area. Gallows tells you his real name is "Irving", and asks that he just be left alone.

Convincing Gallows to tell you his name is one of the most difficult Speech checks in the game. Even with a 100 Speech and 9 Charisma skill, you may not have a 100% chance of passing the check. With all expansion packs and latest updates added, the player needs 100 Speech and 10 Charisma to get the Speech check success chance to 100%.